1. Field of the Invention
This invention relates to catalysts suitable for use particularly in the cracking of mineral oils.
2. Description of the Prior Art
Middle distillates, typified by kerosine and light gas oil, have recently been in strong and growing demand. These distillates are derived generally by atmospheric distillation of crude oil and alternatively by hydrocracking of mineral oils such as crude oil, liquefied coal gas, deasphalted oil, shale oil, vacuum gas oil, and residual oils including atmospheric residues, vacuum residues and the like.
Hydrocracked lubricant base oils have also received high credit for their greater values of viscosity index and higher rates of yield.
Hydrocracking converts mineral oils, because of their varying fractions, to a number of petroleum products by the use of many different catalysts. Most commonly employed are catalysts made up of porous inorganic oxides such as alumina and silica-alumina, and active metals of Group VI such as molybdenum and tungsten and of Group VIII such as cobalt and nickel. To attain improved hydrogenation and cleavage qualities, this catalyst system has been fluorinated by impregnation or coprecipitation in aqueous solution as disclosed for instance in Japanese Patent Publication No. 46-6507, or by deposition in gaseous phase as taught in U.S. Pat. No. 3,457,188. Such prior catalysts, however, are not wholly satisfactory as they are catalytically not so active and less selective.